1. Field of the Invention
This invention relates to in-ground conduits through which above ground access can be gained to below surface objects and/or spaces and, more particularly, to a method for covering a surface opening through which access to the conduit is gained.
2. Background Art
It is common for public utilities to install wiring, conduits for communication of fluids and gases, etc., below surface grade. By so doing, the supply lines and pipes, operating components, such as valves and switches, controls, etc., are conveniently placed so that they are not visible to the public, do not interfere with surface traffic, and are not prone to being damaged and/or tampered with. Below surface objects and spaces have been in place for many decades on both public and private lands.
While below surface installations afford a great convenience to the utilities and other entities, both public and private, access to the below surface components by the controlling entities is inherently limited. It is known to install conduits that permit access to critical components and/or locations through an upper opening in the conduit. For example, control valves for buried pipes are commonly installed at below surface locations and made accessible for operation through vertical conduits. Removable covers are incorporated into the conduits to block the surface access opening to the conduit. By removing the cover, an individual can access the valve through the conduit, as to effect operation and/or or repair thereof.
Likewise, access to below surface spaces and tunnels is commonly gained through a conduit that is selectively blocked by a manhole cover. These conduits are large enough to allow individuals to pass therethrough to perform any needed below surface operations, be they in the form of installation, maintenance, adjustment, etc.
These various conduits are commonly installed on public right-of-ways, although this is not a requirement. Typically, conduits for valve access and larger conduits on which manhole covers are placed, are often seen on paved roadways. This is common since utilities will regularly install their lines/pipes, etc. beneath and along the extent of a paved highway as it is being constructed.
An objective of installers of these conduits, and covers therefor, is that the cover remain flush with the above ground surface that is exposed. Ideally, vehicular traffic can move over the covers without any sensing of their presence as would occur in the event that there is any difference in height between the cover and the road surface, be the cover either above or below the road surface.
At the time roads are initially constructed, the conduits can be incorporated so that the covers at the surface openings can be precisely situated flushly with the road surface. However, subsequent events may alter this relationship. It is not uncommon for pavement to settle over time around the conduit. Alternatively, the pavement may buckle or elevate around the same conduit. Repaving of surfaces may also change the relationship between the cover and the road surface. As one example, it is common for repaving operations to involve removal of a partial thickness of an exposed asphalt layer, which is subsequently replaced by a thicker layer that produces a step between the road surface and the cover, be it a manhole cover, a cover for a valve, etc. The difference in height may be such that the particular entity responsible for controlling the roadway chooses not to make any modification. As a result, those travelling over the roadway may sense a significant bump as vehicle wheels transition over the steps.
It is also known to provide a cover support that is separate from the conduit and that can be raised and lowered relative to the conduit, as through a threaded connection therebetween. To accommodate a variation in the road surface height, the cover support structure can be turned to be raised or lowered as required to cause the cover to flushly meet the road surface. In the former situation, there may be produced a significant gap over the compacted sub-surface layer(s) supporting the asphalt or concrete that defines the exposed road surface. This gap allows for the ingress of moisture that may cause shifting of a cover support and/or conduit under conditions wherein the moisture is repeatedly frozen and thawed. This gap may in any event create a non-uniform compaction around the cover that may cause vertical and/or lateral shifting of the conduit that produces a skewed or vertically offset alignment between the cover and road surface.
Various other makeshift procedures have been practiced to reseat the covers after roadways are broken up, repaved, or otherwise modified so as to alter the height of the upper surface thereof.
Another problem that has plagued this industry is the generation of rattling noise as manhole covers and other covers are traveled over by vehicles and thereby shifted relative to a cooperating support. For example, a manhole cover that is not flushly seated around its entire perimeter may tend to tip back and forth each time it is traveled over. As a vehicle wheel encounters one location, the cover is tipped down into contact with a metal support. Continued travel causes the diametrically opposite location to shift downwardly against the metal support such that two distinct sounds may be heard at each pass.
The industry continues its efforts to develop systems on roadways and other locations that will consistently permit flush mounting of covers at surface access openings and that can be adapted to maintain this flush relationship even when the primary surface grade is changed. The industry also continues to seek out structure that will avoid offensive rattling between metal components as vehicles move over these various covers. The industry has to date contended with the above noted problems since viable solutions thereto are not commercially available.